A particular area of application of a padlock is in the field of occupational safety. There is the risk in relation with the servicing of industrial plants, for example of a production machine, that the industrial plant deactivated for the purpose of servicing work is activated again by accident while the servicing work is still continuing. A substantial danger for the service engineer can result from this. It is therefore customary that the service engineer moves a switch associated with the industrial plant to an OFF position for the duration of the servicing work and secures it in this position, i.e. the switch is directly blocked or access to the switch is blocked. The named switch is typically an energy supply switch, for example a main electrical switch of a control device or of an energy supply device of the industrial plant (e.g. power switchbox). Alternatively to this, the named switch can, for example, be a valve of a liquid line or of a gas line.
In order effectively to avoid an accidental activation of the industrial plant by another person, each service engineer hangs a padlock on the named switch or on a blocking device associated with the switch before starting his work and locks said padlock. The switch is hereby secured in its OFF position, i.e. the switch cannot be moved accidentally back into an ON position by another person. When the service engineer has ended his work, he unlocks the padlock again and releases it from the switch. Each service engineer usually has his own individual padlock (or a plurality of his own individual padlocks) associated with him. This procedure is also called a lockout. The padlock used is accordingly called a lockout lock.
So that a plurality of service engineers can block and release the switch again independently of one another, a plurality of receivers (e.g. eyelets) can be provided at the switch for hanging a plurality of lockout locks. If only a single receiver for a lockout lock is provided, a securing claw can be used which is hung into the respective eyelet of the switch or of the associated blocking device and which in turn has a plurality of hang-in eyelets for a respective padlock. Only when the last padlock has been removed from the securing claw can the securing claw be removed from the switch so that it can again be brought into the ON position.
It is known in connection with such a securing of a switch of an industrial plant to equip the lockout lock used with a housing of plastic, with a hoop being displaceably held at the lock housing and with a lock cylinder being arranged in the lock housing. The lock cylinder can selectively be brought from an open position into a latching position to latch the hoop to the lock housing after the hoop has, for example, been hung into an eyelet of the switch. By forming the lock housing from plastic, a particularly light padlock results which is of advantage in the use as a lockout lock since the service engineers occasionally carry a plurality of lockout locks simultaneously. A housing of plastic can also contribute to a desired electrical insulation. By the use of a plastic housing, there is furthermore a particularly simple possibility of color marking the padlock. The smaller stability of a plastic housing in comparison with a lock housing made of metal does not represent any serious disadvantage in a lockout lock since the padlock only serves the purpose of securing a switch against unintentional actuation, but not, for example, as theft protection.
It is furthermore known by prior use by the Safety Padlock No. 411 of the Masterlock® company to design the lock housing as elongate, i.e. to configure a length of the lock housing as substantially larger than a maximum width of the lock housing. It is thereby possible to apply wording in two languages, for example, to such an enlarged surface of the lock housing which warns against the removal of the lockout lock. For instance, a warning in English can be printed in the upper region of the lock housing and a corresponding warning in Spanish can be printed in the lower region of the lock housing, for example. Alternatively, a photo of the respective service engineer person can be applied to the lock housing so that it is immediately recognizable who has attached the lock. To be able to extend the lock housing of the padlock in this manner, a coupling element can be provided in the lock housing which connects the latching member and the cylinder core to one another in a rotationally fixed manner. The coupling element in this respect has to be configured the longer the length of the lock housing is.
In the Safety Padlock No. 411 known by prior use, the coupling element and the latching member are configured in one part as a zinc die-cast part, with the coupling element being made as a full cylinder. The coupling element is supported on reinforcement ribs of the lock housing, which is known, for example, from U.S. Pat. No. 5,755,121. The lock housing is formed from plastic and is in this respect composed of two halves.
Both a manufacture by an injection molding process and a welding of the halves of a lock housing suffer from large tolerances, which can have the result that the reinforcement ribs jam the coupling element or the coupling element is seated too loosely between the reinforcement ribs. Consequently, a high frictional force can be generated, whereby the padlocks are relatively stiff in operation. In addition, particularly with large lengths of the coupling element, a canting of the coupling element at the cylinder jacket surface can occur. In addition, a solid coupling element produced from metal greatly increases the weight of the padlock in a disadvantageous manner.
Alternatively, the cylindrical coupling element can be guided, for example, in a cylinder jacket surface, whereby a support of the coupling element along the total cylinder jacket surface results. Due to the large surfaces rubbing against one another, a high frictional force is generated which can likewise result in padlocks which are stiff in operation.